Re: [PATCH v3] man/man7/socket.7: fix documentation for SO_ATTACH_REUSEPORT_EBPF

[Alejandro Colomar <alx@kernel.org>]

[-- Attachment #1: Type: text/plain, Size: 3229 bytes --]

Hi Vincent, Craig,

On Tue, Dec 02, 2025 at 10:49:03AM -0500, Craig Gallek wrote:
> On Mon, Dec 1, 2025 at 2:57 PM Vincent Bernat <vincent@bernat.ch> wrote:
> >
> > When using eBPF, there are two possible cases depending on the program
> > type. Only the first case was described. In the second case, the program
> > should not return an index, but a decision (SK_PASS/SK_DROP). The socket
> > should be selected using the sk_select_reuseport helper.
> >
> > Cc: Craig Gallek <kraig@google.com>
> > Signed-off-by: Vincent Bernat <vincent@bernat.ch>
> > ---

I have applied the patch, with some important reorganization of the
text.
<https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/commit/?id=41788bdd42312828532c4ddbadc0a4d28426d4fd>

> >  man/man7/socket.7 | 23 ++++++++++++++++++++---
> >  1 file changed, 20 insertions(+), 3 deletions(-)
> >
> > diff --git a/man/man7/socket.7 b/man/man7/socket.7
> > index b4d58a23d5da..e4e85dc9345d 100644
> > --- a/man/man7/socket.7
> > +++ b/man/man7/socket.7
> > @@ -354,20 +354,34 @@ the sockets in the reuseport group (that is, all sockets which have
> >  .B SO_REUSEPORT
> >  set and are using the same local address to receive packets).
> >  .IP
> > -The BPF program must return an index between 0 and N\-1 representing
> > +The classic BPF program must return an index between 0 and N\-1 representing
> >  the socket which should receive the packet
> >  (where N is the number of sockets in the group).
> >  If the BPF program returns an invalid index,
> >  socket selection will fall back to the plain
> >  .B SO_REUSEPORT
> >  mechanism.
> > -.IP
> >  Sockets are numbered in the order in which they are added to the group
> >  (that is, the order of
> >  .BR bind (2)
> >  calls for UDP sockets or the order of
> >  .BR listen (2)
> >  calls for TCP sockets).
> > +.IP
> > +The extended BPF program can be of two types:
> > +.B BPF_PROG_TYPE_SOCKET_FILTER
> > +or
> > +.BR BPF_PROG_TYPE_SK_REUSEPORT .
> > +In the first case, the extended BPF program must return an index between 0 and N\-1,
> > +like a classic BPF program.
> > +In the second case, it must return an action
> > +.RB ( SK_PASS
> > +or
> > +.BR SK_DROP )
> > +and the
> > +.B bpf_sk_select_reuseport
> > +helper can be used to select the socket which should receive the packet.
> > +.IP
> >  New sockets added to a reuseport group will inherit the BPF program.
> >  When a socket is removed from a reuseport group (via
> >  .BR close (2)),
> > @@ -386,7 +400,10 @@ takes the same argument type as
> >  .BR SO_ATTACH_BPF .
> >  .IP
> >  UDP support for this feature is available since Linux 4.5;
> > -TCP support is available since Linux 4.6.
> > +TCP support is available since Linux 4.6;
> > +support for
> > +.B BPF_PROG_TYPE_SK_REUSEPORT
> > +program type is available since Linux 4.19.
> >  .TP
> >  .B SO_BINDTODEVICE
> >  Bind this socket to a particular device like \[lq]eth0\[rq],
> > --
> > 2.51.0
> 
> Looks good to me, thank you for the clean up!

Thanks!  I took this as an Acked-by.  (I prefer them to be explicitly
stated, though.)


Have a lovely day!
Alex

-- 
<https://www.alejandro-colomar.es>

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]